Heat exchangers are often used to transfer heat between two fluids. For example, in gas turbine engines, heat exchangers may be used to transfer heat between a relatively cold fuel and relatively hot engine oil.
Various types of heat exchangers are known. Some heat exchangers are formed by a stack of laminates, each with portions therein carved out to allow fluid flow. The layers are brazed together to create sealed cavities within a stack. Alternating layers of the heat exchanger are either relatively hot or cold, such that the two fluids are kept separate and have a large surface area available for heat exchange.
Improvements upon heat exchanger design have dealt with ensuring that the heat exchanger stack can withstand thermal expansion and contraction and other stresses, as well as maximizing thermal transfer.
One such improvement associated with maximizing thermal transfer is the use of a so-called “secondary” surface. The “primary” surface is the surface of the laminate along which the fluid flows. “Secondary” surfaces are often built upon the primary surface to facilitate additional heat transfer. For example, secondary surfaces may include pins, fins, vanes, and other structures.